Purple light appears as an intensively purple-coloured light in a cloudless clear sky. It appears at sun elevations between -2� and -5� and is the maximum of the twilight. It is caused by very small dust particles in higher layers of the atmosphere which scatter the sunlight. This is the reason why the purple light is especially intensive after volcanic eruptions, big forest blazes or near big cities.

In rare cases a purple light can also appear opposite the sun that has already sat. But in most cases there are violet, blue and/or green colours forming a significant contrast to the slowly rising twilight wedge.